The present invention relates to a vacuum switch and a vacuum switchgear using the vacuum switch and, more particularly to a vacuum switch most suitable to be made small in size and a vacuum switchgear using the same.
As incoming transformer apparatuses to be made compact, a SF6 gas-insulated switchgear is disclosed in JP A 3-273804, for example. In the switchgear, a circuit breaker, two disconnecting switches, and an earth device are individually manufactured and contained in a unit chamber filled with an insulating gas and a bus chamber arranged in a switch box. In the case where a vacuum circuit breaker is used as this circuit breaker, a movable electrode is moved up and down to a fixed electrode to close and open by an operation device of the circuit breaker. There is also a vacuum circuit breaker, as disclosed in JP A 55-143727. In the vacuum circuit breaker a movable electrode is rotated left and right about a main axis as a supporting point to contact with or separate from a fixed electrode, that is, to close or open. Further, there is a switchgear as disclosed in JP A 9-153320, which is constructed so that while a movable conductor arranged in one vacuum container is roundly moving between a fixed conductor and an earth conductor, the movable conductor moves to a close position, an open position, a disconnecting position and an earth position.
Further, JP A 5-166440 and JP A 3-225718 each disclose a vacuum switch constructed so that a vacuum bulb, an operation mechanism for operating the vacuum bulb and a disconnecting device are contained in a hermetically closed metal box or a switch case.
The SF6 gas insulated-switchgear disclosed in JP A 3-273804 uses a SF6 gas, so that it is required to reduce the SF6 gas in view of a greenhouse effect. Therefore, a switchgear in which the SF6 gas is not used is desired. In the vacuum circuit breaker disclosed in JP A 55-143727, since the container is not grounded, in order to perform maintenance inspection of the incoming transformer apparatuses, it is necessary to take sufficient safety measures such as prevention of re-application of current or voltage from a power source by causing remaining electric charges and induction current to flow into an earth by opening the disconnecting switch provided other than the circuit breaker and grounding the earth switch after opening the circuit breaker. In the circuit breaker, the apparatuses are individually provided, so that it is difficult to make the size of the circuit breaker small. Further, the switchgear disclosed in JP A 9-153320 is excellent in making the size small, however, since the close position, open position, disconnecting position and grounding position are provided in one vacuum container, it has such a disadvantage that all the functions are lost when an accident occurred by any chance. JP A 5-166440 and JP A3-225718 each disclose that the vacuum bulb is contained in the hermetically closed metal box or switch case, however, they do not disclose that the hermetically closed metal box or switch case is made vacuum, and that the hermetically closed metal box or switch case is grounded.
A first object of the present invention is to provide a vacuum switch which is made small in size and a switchgear using the vacuum switch.
Another object of the present invention is to provide a vacuum switch which can be suited for diversification of apparatuses and a switchgear using the vacuum switch.
Still another object of the present invention is to provide a vacuum switch which is improved in assemblage and a switchgear using the vacuum switch.
Further still another object of the present invention is to provide a vacuum switch which is improved in insulation and a switchgear using the vacuum switch.
In order to attain the above objects, a vacuum switch of the present invention comprises a first vacuum container containing therein a fixed electrode and a movable electrode of a circuit breaker, and a second vacuum container which is electrically insulated from the first vacuum container and grounded and contains therein the first vacuum container. The first vacuum container is communicable in vacuum with the second vacuum container, for example, through a small gap between an insulator forming a part of the first vacuum container and a conductor connected to a fixed or movable conductor and passing through the insulator. Thereby, the vacuum of the two vacuum containers reaches an equilibrium state under normal condition and is stable.
A wall of the first vacuum container containing therein the fixed electrode and the movable electrode of the circuit breaker and a wall of the second vacuum container are arranged at such a distance that the both walls are lower in potential than the potential of a bus, or at a relatively small distance. Particularly, they are arranged to keep such a distance that the potential of the wall of the first vacuum container becomes intermediate potential between the potential of the bus and the earth potential.
The second vacuum container also contains therein an insulator fixed both to the conductor electrically connected to the circuit breaker and to a movable rod for operating the circuit breaker to open and close.
A vacuum switch of the present invention comprises a first vacuum container containing therein a circuit breaker, a second vacuum container containing therein the first vacuum container and grounded, and a third vacuum container connected to the second vacuum container, containing therein a disconnecting switch and grounded. The first vacuum container is communicable in vacuum with the second vacuum container through a gap, however, the vacuum of the third vacuum container is isolated from the vacuum of the first and second vacuum containers.
The second vacuum container also contains therein an insulator fixed both to the conductor electrically connected to the circuit breaker and to a movable rod for operating the circuit breaker to open and close. Further, the disconnecting switch and the circuit breaker, preferably, the insulator fixed to the conductor and the movable rod also are arranged in a substantially straight line.
The vacuum switch is constructed so that a disconnecting switch and an earth device are contained in the third vacuum container. Further, at least one vacuum container containing the first vacuum container is provided between the first and second vacuum containers.
Further, a vacuum switchgear according to the present invention has switches as mentioned above of the number corresponding to three phases or more, and necessary elements such as a protective relay device and an operation box arranged in a metal box.